Synthesis of 5,6-Dihydro-4H-pyrrolo[1,2-b]pyrazoles and Homologs from 5-Substituted 2-(Alkynyl)tetrazoles via Microwave-Induced Intramolecular Nitrile-Imine–Alkyne 1,3-Dipolar Cycloaddition

Abstract

Microwave irradiation of 2-alkynyl-5-(phenyl or alkyl)tetrazoles afforded 2-(phenyl or alkyl)-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazoles via intramolecular [3+2] cyclization of nitrile-imine intermediates. In the present method, use of 5-alkyltetrazoles as the starting materials was more advantageous, because it was difficult with conventional photoreactions. From 2-phenylalkynyl-5-methylthio-1H-tetrazoles, the reaction efficiently produced 2-methylthio-3-phenyl-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazoles. The procedure using the methylthio group was applied to the total synthesis of three naturally-occurring withasomnines. The method was extended to the construction of molecules in which bicyclic pyrazoles were fused to six- to eight- membered rings.

Constructing a graphene-like structure to lower friction sensitivity: Ag(i) complexes based on furan-2,5-dicarbohydrazide

“…[5][6][7] Energetic coordination polymers (ECPs) are obtained by connecting organic ligands and metal ions through coordination covalent bonds, and they have become the focus of many scholars in the field of primary explosives because they have more outstanding advantages: (1) they can be prepared using relatively simple methods; (2) by changing the combination of ligands and metal ions, the overall performance can be adjusted and optimized to meet the requirements in different scenarios. [8][9][10][11] With the unremitting efforts of scholars, more and more ECPs have been designed and synthesized. However, the problem is that the two most important performance targets, high energy and insensitivity, cannot be achieved at the same time.…”

“…5–7 Energetic coordination polymers (ECPs) are obtained by connecting organic ligands and metal ions through coordination covalent bonds, and they have become the focus of many scholars in the field of primary explosives because they have more outstanding advantages: (1) they can be prepared using relatively simple methods; (2) by changing the combination of ligands and metal ions, the overall performance can be adjusted and optimized to meet the requirements in different scenarios. 8–11…”